Acylation of dichlorothiophene



agent. However, an excess of oneof the reactantsY appears to be desirable, resulting in an increased yield of product. The reaction vvrate is largely a function of the temperature. increasing with increasing temperature, the upper limit of temperature being dependent on the boiling point of the reactants at the specific pressure of the reaction'.

In general, temperatures between about `30 C;

and about 150 C. and pressures betweenaboutlv l and about 10 atmospheres have been found satisfactory n for effecting' "the acylation reaction.

Ordinarily, a pressure lsuiiicient to maintain the reactants inthe liquid phaseis" used and this is 'more or less dependent 'on the vparticular temper to be understood that these reaction Variables aref.

more or'less interdependent. Generally, however, the reaction period required for theV acylation vprocess to be complete will be between about l.

and about -10 hours.

The' acylated chlorothiophenes produced in accordance withv this invention are useful in prepa-- ration of'insecticides, as solvents, dye intermediates, addition compounds Yfor petroleum fractions, 'plasticizers, odorants, perfume diluents, resin in-v termediates and intermediates for chemical syn-- thesis. v YThe following examples will serve t`o illustrate the process of this invention Without limiting the.` same:

Example 1 To a mixture of v355.5 gramsr (3 moles) of 2- chlorothiophene and 377 grams (3.5 moles) of 95 per cent acetic anhydride were added 35 grams; of S5-.per cent orthophosphoric acid. The mix-l turewas heated' at 13D-.135" C, for, three hours.. After cooling, 500 millimeters of water were added and the mixturewas distilled until alll of the 2- chlorothioph'ene-present in the reaction product mixture wasrecovered. 1 The mixture was diluted With benzene; Washed to remove acetic `acid present and nally washed with .dilute sodium carbonate solution until neutral. the benzene, the product was distilled, under reduced pressure' tov yield 337 grams ('70 per cent yield) of 2-acetyl-5-chlorothiophene having a boiling point at 4 millimeters pressure of 88 C. The product .was recrystallized from alcohol and water to give a pure White product having a melting,poi ntjof46.5.l7 C. A mixed melting point ofthisproduct with an authentic sample of 2- acetyl-5-ch1orothiophene showed no depression. The oxime of the product was prepared by standard procedures and after recrystallization from alcohol and Water it melted` at 159.5-160-.5 C. Analysis of the oxime indicated a nitrogen'content of '7.84 per cent which is identical with the calculated nitrogen content.

Example 2 To a'mixture of 153`grams (1 mole) of 2,5-dichlorothiophene and'214 grams (2 moles) of 95 per cent acetic anhydride heated to 60 C. were added grams of 85 per cent orthophosphoric acid. The reaction vmixture was maintained at 120 C. for two hours. Evolution of hydrogen chloride gas was noted and toward the end of the reaction period traces of hydrogen sulfide were evolved. After 'cooling'v the reaction product mixture', waterwas added and -120 grams of unreacted 2,5-dichlorothiophene were recovered by steam distillation. Upon cooling the remaining mixture, crystallir'zationY took place in the organic layer; the Water layer was decanted and the resulting product 'freed o'facetic acid by digesting with warm v Water. Twenty-nine grams of product were obtained; which, after recrystallizing from petroleum ether, melted at 4GB-47 C. A mixed melting point with an authentic sample of 2- v acetyl-5-chlorothiophene showed no depression.

a Analysis of the product indicated a chlorine content of 22.23 per cent and a sulfur content ofi 20.31 per cent. The calculated chlorine and sul-v fur contents for 2-acetyl-5-chlorothiophene were 22.17 and 19.93 per cent respectively. The oxime of the product was prepared by standard procef dures and melted at 159. 5-160.5 C.

1. A process for converting a dichlorothiophene by nuclear acylation thereof into an acyl mono-- chlorothiophene comprising reacting said dichlo rothiophene with an acylating agent in the pres ence of phosphoric acid.

, 2. A process vfor converting a mixture of monoand dichlorothiophenes by nuclear acylation thereof into an acylation product consisting of an acyl monochlorothiophene comprising reacting lsaid mixture with an acylating agent in the presence of phosphoric acid. n

3. A process for converting a dichlorothiophene by. nuclear acylation thereof into an acyl monochlorothiophene .comprising reacting said dichlorothiophene with an acylating agent in the presence of between about 0.1 and about 8 per cent by weight of phosphoric acid.

4. A process for converting a mixture of monoand v dichlorothiophenes by nuclear acylation thereofinto an acylation product consisting of an acylxnonochlorothiophene comprising reactingV said mixture with `an acylating agent in the presence of about 0.1 to about per cent by weight of phosphoric acid.

5. A process for converting a dichlorothiophene by nuclear acylation thereof into an acyl monochlorothiophene comprising reacting said dichlorothiophene with a carboxylic acidanhydride in the presence of phosphoric acid.

6. A process for converting a dichlorothiophene by nuclear acylation thereof into an acyl monochlorothiophene comprising reacting said dichlorothiophene with an acyl halide in the presence of phosphoric acid.

7. A process forconverting a dichlorothiophene by nuclear acylation thereof into an acetyl monochlorothiophene comprising reacting said dichlorothiophene with acetic anhydride in the presence of phosphoric acid.

l HOWARD D. HARTOUGH.

y ALVIN I. KOSAK.

REFERENCES CITED The followingreferences are of record in the lle of this patent:

Berkman,"Catalysis, pages 657, 658. Excerpt on Condensation.v Reinhold Pub. Co., 1940.

Fieser and Fieser, @Organic Chemistry, page 536. Heath, 1944. lj

Thomas', Anhydrous Aluminum Chloride in Organic Chemistry, page 373. Reinhold Pub. 

